1. Field of the Invention
The present invention relates to a water treatment apparatus designed to produce tap water and to treat wastewater or underground water and industrial wastewater, etc., and more particularly, it relates to a water treatment apparatus in which wastewater is highly purified using ultraviolet radiation together with an oxidizer such as, for example, ozone, etc.
2. Description of the Related Art
A water treatment apparatus using an oxidizer, such as ozone, and ultraviolet radiation in combination decomposes substances to be treated such as organochlorine compounds in wastewater using radical seeds, such as hydroxyl radicals, etc., which are produced by irradiating the oxidizer, such as ozone, with ultraviolet light.
As such a water treatment apparatus, it has hitherto been proposed to diffuse an ozone gas into wastewater that flows in a cylindrical reaction tank, and to further irradiate ultraviolet light from an ultraviolet lamp onto the water, whereby substances to be treated in the wastewater are decomposed, thus discharging the water thus treated as effluent.
In a known water treatment apparatus, it was general that an ultraviolet lamp was installed in the center of a water tank of a cylindrical, hexahedral, or other like configuration. In addition, as an oxidizer mixing means, there has generally been used a scheme in which a diffuser or the like is installed in a water tank into which wastewater is caused to flow, so that an ozone gas is dispersed as gas bubbles into the wastewater thereby to mix and dissolve ozone with and into the water (see, for example, a first patent document: Japanese patent application laid-open No. H5-192673).
With such a known water treatment apparatus, using the diffuser as an oxidizer mixing means, however, there was a limit to the control of the diameters or sizes of gas bubbles, thus making it difficult to increase gas-liquid interfacial area to any satisfactory extent. Therefore, the dissolution rate of ozone was slow, and there was a problem that the substances to be treated were not decomposed at a high efficiency in a short period of time.
Furthermore, since the known water treatment apparatus has the ultraviolet lamp installed in the center of the water tank of the cylindrical, hexahedral, or other like configuration, there was another problem that the strength of ultraviolet light required for the treatment of the wastewater was not obtained in an area apart from the ultraviolet lamp, resulting in a low decomposition rate of the substances to be treated.